In the context of a transaction using HTTP, authentication is a method for a program or a web browser at a client computing device to provide user credentials which may include a user name and a password each time while making a request. A HTTP header based authentication requires a server to send back HTTP 401/407 challenge to browser for collecting user's authentication credentials or token. The general process which is followed is the web server sending a HTTP 401/407 challenge for each new TCP connection and web-browser replying with user's credentials or token as response to the challenge.
However, each 401/407 challenge attempt adds latency by creating one or more than one extra round trip time between the client and the server. It also adds to the processing overhead on server side as server needs to verify the received credential or token for each request.